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ST10F269ZX 数据表(PDF) 77 Page - STMicroelectronics |
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ST10F269ZX 数据表(HTML) 77 Page - STMicroelectronics |
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77 / 184 page ![]() ST10F269 12 - PARALLEL PORTS 77/184 12.7.1 - Alternate Functions of Port 4 During external bus cycles that use segmentation (address space above 64K Bytes) a number of Port 4 pins may output the segment address lines. The number of pins that is used for segment address output determines the external address space which is directly accessible. The other pins of Port 4 may be used for general purpose I/O. If segment address lines are selected, the alternate function of Port 4 may be necessary to access external memory directly after reset. For this reason Port 4 will be switched to this alternate function automatically. The number of segment address lines is selected via PORT0 during reset. The selected value can be read from bitfield SALSEL in register RP0H (read only) in order to check the configuration during run time. The CAN interfaces use 2 or 4 pins of Port 4 to interface each CAN Modules to an external CAN transceiver. In this case the number of possible segment address lines is reduced. The Table 21 summarizes the alternate functions of Port 4 depending on the number of selected segment address lines (coded via bitfield SALSEL) Table 21 : Port 4 Alternate Functions Port 4 Standard Function SALSEL = 01 64K Bytes Alternate Function SALSEL = 11 256K Bytes Alternate Function SALSEL = 00 1M Byte Alternate Function SALSEL = 10 16M Bytes P4.0 P4.1 P4.2 P4.3 P4.4 P4.5 P4.6 P4.7 GPIO GPIO GPIO GPIO GPIO/CAN2_RxD GPIO/CAN1_RxD GPIO/CAN1_TxD GPIO/CAN2_TxD Segment Address A16 Segment Address A17 GPIO GPIO GPIO/CAN2_RxD GPIO/CAN1_RxD GPIO/CAN1_TxD GPIO/CAN2_TxD Segment. Address A16 Segment Address A17 Segment Address A18 Segment Address A19 GPIO/CAN2_RxD GPIO/CAN1_RxD GPIO/CAN1_TxD GPIO/CAN2_TxD Segment Address A16 Segment Address A17 Segment Address A18 Segment Address A19 Segment Address A20 Segment Address A21 Segment Address A22 Segment Address A23 Figure 30 : Port 4 I/O and Alternate Functions Port 4 Alternate Function a) General Purpose Input / Output b) Segment Address Lines Cans I/O and General Purpose Input / Output P4.7 P4.6 P4.5 P4.4 P4.3 P4.2 P4.1 P4.0 A23 A22 A21 A20 A19 A18 A17 A16 CAN2_TxD CAN1_TxD CAN1_RxD CAN2_RxD - - - - |
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